Cutting dies having a steel rule configuration have been in use since 1896, when it was accidently discovered that creasing rules being used in a printing operation could be used to cut paper under sufficient pressure. Improvements in using the rules as a cutting die were achieved by sharpening the top of the rule to a knife edge. In recent times, cutting dies have become very complex, and thousands of different dies are now in use.
Die cutting operations have similarities to printing operations, wherein the knife edge passes through the material being cut and comes in contact with a hardened platen. In actuality, however, the knife makes hard contact in various areas along the cutting edge due to the irregularities in the platen, bearings, linkages, etc. These irregularities lead to wear or flattening of portions of the knife edge. Softening the platen would not provide a solution to this problem. While a softer platen would reduce knife edge wear, it would also result in poor die cutting, which would in turn require excessive press pressures.
Knife edge wear is a serious problem in the trade, since a flattened or worn blade results in poor die cutting. Worn blades must be discarded, which is expensive from a materials replacement and labor standpoint. In addition, the replacement of the die results in down time.
To some extent, knife wear can be minimized by adjustments known in the industry as "make-ready". The make-ready adjustments comprise the application of shims under the platen or at the base of the die where cutting contact is incomplete. These make-ready adjustments, however, are at best a mediocre solution to the problem. These adjustments are labor intensive, and really do not address the problem of knife edge wear in a satisfactory manner.
Make-ready has been a procedure in the industry for a long time, thus indicating a long felt need for an improved cutting die.